Alkaloids ars


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Alkaloids ars

  1. 1. Mr. A.R.Surana Assistant professor S.M.B.T. College of Pharmacy, Nashik-422403 9/6/2013
  2. 2. Definition: the term “alkaloid” (alkali-like) is commonly used to designate basic heterocyclic nitrogenous compounds of plant origin that are physiologically active. Derived from amino acids. Alkaloids
  3. 3. DEVIATION FROM DEFINITION: • Basicity: Some alkaloids are not basic e.g. Colchicine, Piperine, Quaternary alkaloids. • Nitrogen: The nitrogen in some alkaloids is not in a heterocyclic ring e.g. Ephedrine, Colchicine, Mescaline. • Plant Origin: Some alkaloids are derived from Bacteria, Fungi, Insects, Frogs, Animals. • Biosynthesis: Some alkaloids are not derived from amino acids e.g purine, steroidal alkaloid .
  4. 4. QUALITATIVE CHEMICAL TESTS FOR ALKALOIDS General tests answered by all alkaloids are as follows: 1. Dragendorff’s test: To 2–3 mL of the alkaloid solution add few drops of Dragendorff’s reagent (potassium bismuth iodide solution). An orange brown precipitate is formed. 2. Mayer’s test: To 2–3 mL of the alkaloid solution add few drops of Mayer’s reagent (potassium mercuric iodide solution). White brown precipitate is formed. 3. Hager’s test: To 2–3 mL of the alkaloid solution add few drops of Hager’s reagent (saturated solution of picric acid). Yellow precipitate is formed. 4. Wagner’s test: To 2–3 mL of the alkaloid solution add few drops of Wagner’s reagent (iodine– potassium iodide solution). Reddish brown precipitate is formed.
  5. 5. Physical Properties: I- State: • Most alkaloids are crystalline solids. • Few alkaloids are amorphous solids e.g. emetine. • Some are liquids that are either: Volatile e.g. nicotine and coniine, or Non-volatile e.g. pilocarpine and hyoscine. II- Color: The majority of alkaloids are colorless but some are colored e.g.: • Colchicine and berberine are yellow. • betanidine is orange. • The salts of sanguinarine are copper-red.
  6. 6. III- Solubility: • Both alkaloidal bases and their salts are soluble in alcohol. • Generally, the bases are soluble in organic solvents and insoluble in water Exceptions: – Bases soluble in water: caffeine, ephedrine, codeine, colchicine, pilocarpine and quaternary ammonium bases. – Bases insoluble or sparingly soluble in certain organic solvents: morphine in ether, theobromine and theophylline in benzene. • Salts are usually soluble in water and, insoluble or sparingly soluble in organic solvents. Exceptions: – Salts insoluble in water: quinine monosulphate. – Salts soluble in organic solvents: lobeline and apoatropine hydrochlorides are soluble in chloroform
  7. 7. IV- Isomerization: • Optically active isomers may show different physiological activities. l-ephedrine is 3.5 times more active than d-ephedrine. l-ergotamine is 3-4 times more active than d-ergotamine. d- Tubocurarine is more active than the corresponding l- form. • Quinine (l-form) is antimalarial and its d- isomer quinidine is antiarrythmic. • The racemic (optically inactive) dl-atropine is physiologically active.
  8. 8. Chemical Properties  Most of the alkaloids are basic in nature, due to the availability of lone pair of electrons on nitrogen.  The basic character of the alkaloid compound is enhanced if the adjacent functional groups are electron releasing.  The alkaloid turns to be neutral or acidic when the adjacent functional groups are electron withdrawing like amide group which reduces the availability of the lone pair of electron.  Their salt formation with an inorganic acid prevents many a time their decomposition.  In the natural form, the alkaloids exist either in Free State, as amine or as salt with acid or alkaloid N-oxides.  The alkaloid may contain one or more nitrogen and exist in the form of • Primary amines R-NH2 e.g. Norephedrine • Secondary amines R2-NH e.g. Ephedrine • Tertiary amines R3-N e.g. Atropine • Quaternary ammonium salts R4-N e.g d-Tubocurarine
  9. 9. Distribution in Plant • All Parts e.g. Datura. • Barks e.g. Cinchona • Seeds e.g. Nux vomica • Roots e.g. Aconite • Fruits e.g. Black pepper • Leaves e.g. Tobacco • Latex e.g. Opium
  10. 10. Extraction of alkaloids 1. Stass otto method Powdered plant material Defatted with non-polar solvent Defatted plant material Moist with water and treated with NH3, Dil. Lime solution (Free Alkaloid) Extracted with organic solvent like chloroform, ether Extract, Concentrate it Dissolved in Dil. Acid (Alkaloidal salt) Aqueous phase Organic phase impurities Basified with ammonia or sodium Bi-carbonate or Dil. KOH Aqueous phase Organic phase(Free Alkaloid) Evaporate to dryness Crude Alkaloids
  11. 11. Extraction of alkaloids 2. Manske’s method Powdered Crude material Defatted with non-polar solvent Defatted Crude material Extract with methanol Methanol Extract Concentrate Dissolve in water and Acidified it upto pH 2 (Alkaloidal salt) Steam Distillation to remove traces of methanol Stand for several days in refrigerator OR boiled with paraffin Filter Filtrate Shake with organic solvent like chloroform or ether Aqueous phase (Alkaloidal salt) Organic phase Basified with ammonia or sodium Bi-carbonate or Dil. KOH Aqueous phase Organic phase Evaporate to dryness Crude Alkaloids
  12. 12. Purification of Alkaloids 1. Direct crystallization from solvent 2. Repeated acid base treatment 3. Fractional crystallization 4. Chromatographic techniques 5. Gradient pH technique Ephedrine & Pseudoephedrine Oxalates Crystallization from water Ephedrine Oxalate Crystals Pseudoephedrine Oxalate Solution Atropine & Hyoscyamineine Oxalates Crystallization from Acetone/Ether Atropine Oxalate Crystals Hyoscyamine Oxalate Solution
  13. 13. Classification of alkaloids A) True alkaloids Sr. no. Type Structure Examples 1. Pyrrole and pyrrolidine N H N H e.g. Hygrine, coca species 2. Pyiridine and piperidine N N H e.g. Arecoline, anabasine, lobeline, conine, trigonelline 3. Pyrrolizdine N e.g. Echimidine, senecionine, seneciphylline 4. Tropane N e.g. Atropine, hyoscine, hyoscyamine, cocaine, pseudopelletirine 5. Quinoline N e.g. Quinine, quinidine, cinchonine, cupreine, camptothecine 6. Isoquinoline N e.g.Morphine, codeine, emetine, cephaline, narcotine, narceine, d- tubocurarine Chemical classification
  14. 14. 7 Indole N H e.g. Erotamine, ergotametriene, reserpine, vincristine, vinblastine, strychnine, brucine 8 Imidazole N N H e.g. Pilocrpine, isopilocarpine, pilosine 9 Norlupinane N e.g. Cystisine, laburinine 10 Piporphine (reduced isoquinoline napthalene) N e.g. Boldine
  15. 15. B) PROTOALKALOID 1. Alkyalamine HO NH Ephedrine, Pseudoephedrine C) Pseudoalkaloid 1. Purine N NN HN e.g. Caffeine, thophylline, theobromine 2. Steroidal e.g. Solanidine, conessine, protoveratrine 3. Diterpene C20H32 e.g. Aconitine, aconine, hypoaconine
  16. 16. Biosynthetic classification 1. Ornithine derived alkaloids e.g. Pyrrolidine alkaloid-nicotine Tropane alkaloid – Atropine, hyosyamine, coacaine 2. Lysine derived alkaloids e.g. Piperidine and pyridine alkaloid – conine, lobaline, arecoline Quinazolidine alkaloid- lupinine 3. Tyrosine derived alkaloids e.g. Isoquinoline alkaloid – morphine, codeine, emetine, cephaline, berberine, d- tubocurine Amino alkaloid- colchicine 4. Tryptophan derived alkaloids e.g. Indole alkaloid- ergot alkaloid, vincristine, vinblastine, reserpine, strychnine, physostigmine, strychinine, brucine Quinoline alkaloid – cinchonine, quinine, quinidine, camptothecin 5. Histidine derived alkaloids e.g. Imidazole alkaloid – Pilocrpine 6. Phenylalanine derived alkaloids e.g. Amino alkaloid- Ephedrine
  17. 17. Pharmacological classification 1. Narcotic analgesic e.g.Morphine 2. Antimalerial e.g. Quinine 3. Reflux excitability e.g.Strychnine 4. Respiratory stimulant e.g.Lobeline 5. Neuralgia e.g. Aconitine 6. Oxytocic e.g. Erogotometrine 7. Bronchodilator e.g. Ephedrine, vasicine 8. Anticholinergic e.g. Atropine 9. CNS stimulant e.g. Caffeine 10. Antitussive e.g. Codeine 11. Antiarrythmic e.g.Quinidine 12. Antihypertensive e.g. Reserpine 13. Anticancer e.g. Vincristine 14. Antiglucoma e.g. Pilocarpine
  18. 18. Biosynthesis of indole alkaloids
  19. 19. Biosynthesis of Isoquinoline alkaloids
  20. 20. Biosynthesis of Tropane alkaloids
  21. 21. Biosynthesis of Quinoline alkaloids